The Thrift Savings Plan, or TSP, is a kind of defined contribution retirement plan for employees of the federal government, including members of the uniformed services (Army, Navy, Air Force, Marine Corps, Coast Guard, Public Health Service, and the National Oceanic and Atmospheric Administration, including the Ready Reserve or National Guard of those services.)

They work much the same way as 401(k) plans: you can opt to divert part of your salary into the plan, and the money is automatically deducted from your paycheck before taxes are taken out. The money grows tax-deferred until it's withdrawn, and then Uncle Sam comes calling.